"Jeff? How did you... How are you so small? And why were you in my undies?"
Jeff, unaware of what to say, stutters out "I-I don't know! I was sitting on m-my bed, and then suddenly appeared in there!", silently praising himself for his last-minute lie. It was partially true though.
"Alright then... Although, I can't let you run around at this size! You're so small, you could get stepped on! Though, where should I keep you..."
After thinking for a moment, Diana decides that the best course of action would be to keep him where nobody would expect; Her sister's diaper. Nobody would expect anything hidden there, except for maybe poop. However, Diana has to wait for the right opportunity to do this; She can't just walk over and drop him in.
Until she found the right timing, she stored him in her own diaper; Neither Megan nor her mom knew she was taking them. Reaching down to put him in, she put him in her Vagina in a way where he couldn't move, feeling pleasure she hasn't felt before while adjusting him.
================ Jeff POV ================
Jeff was in a spot he didn't want to be in; His sister had trapped him in her vagina, while her snug diapers that barely fit alongside her puffy lips press against him. Although he had to admit that it was cozy, and he didn't attempt to escape. He sat in darkness while awaiting Diana's plan...
================ Diana POV ================
Diana had gone downstairs again, only to find Megan on the couch. Knowing her, Diana knew Megan would fall asleep soon, if she hadn't already. In waiting, Diana sits with Megan until the time was right...
========== Time skip; 5 minutes later ==========
After five minutes of watching TV, Megan fell asleep out of boredom. This was now Diana's time to strike. Diana quickly reached down her diaper, and grabbed Jeff out. She then slowly moved him over to Megan, before carefully peeking her diaper open, almost waking her. Diana then carefully drops Jeff in, trying to keep Megan from waking.
When in there, Jeff immediately noticed that Megan's diapers fit better. Although he wasn't aware, he guessed that Mom knew she needed them; Unlike Diana, who merely wears them for comfort. Jeff feels that he should possibly go down there more often! Although, he does still have to admit that Diana's is more cozy..